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030 008 425 4 



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MASSACHUSETTS INSTITUTE OF TECHNOLOGY. 






f* 






REPORT OF THE SECRETARY, j j 



INCLUDING 



REPORTS OF PROF. PICKERING ON" THE PHYSICAL DABORATO 
AND OF PROF. WATSON ON THE MUSEUM OF DESCRIP 
TIVE GEOMETRY AND MACHINERY. 



In conformity with article 16, section 4, of the By-Laws of the 
Corporation, I herewith present the Annual Report of the trans- 
actions and condition of the Institute for the ninth year, 1870-1871. 

There have been held during the year fourteen meetings of the 
Society of Arts ; these have been well attended, and many inter- 
esting communications have been presented, as follows : 

The meetings of November 3d and 17th, 1870, were taken up by 
the appointment of a committee to draw up a new code of By- 
Laws for the Society, the report of the same, and the nomination 
of officers. 

Nov. 17. Mr. F. E. Stimpson made a communication on the 
economy of gas burners. 

Dec. 1. Mr. R. M. Copeland made a communication on the 
utilization of sewage, showing what a great source of agricultu- 
ral wealth is not only thrown away in large cities, but is actually 
converted into a producer of disease by^contaminating the soil, the 
water, and the air. 

Dec. 15. After the election of the committees constituting the 
Council of the Society, Mr. H. P. Langley read a paper, with illus- 
trations, on " Cast Iron, and the manufacture of Rodman guns." 

Mr. Stimpson explained a diagram of the Savery engine used for 
pumping out mines, introductory to a description and illustration 
of an automatic steam-pump for dwelling houses, attached to the 
ordinary range or kitchen stove. 

Jan. 5, 1871. Prof. C. H. Hitchcock, of Dartmouth College, 
read a paper, illustrated by diagrams and a wooden model, on the 



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topography and geology of the Mt. "Washington group in the 
White Mountains, and gave an account of the meteorological 
establishment on Mt. Washington in winter. 

Jan. 19. Mr. F. E. Stimpson illustrated the efficacy of various 
gas burners, with photometric experiments. 

Feb 2. Mr. Rowell exhibited the "Electro-pneumatic Protec- 
tor," applied to a safe, which is claimed as a perfect protection 
against burglars. The safe is surrounded by a case whose double 
walls are exhausted of air; whenever this vacuum is interfered with 
by opening the door, or making even the finest perforation in the 
case, an electric current is closed, ringing an alarm; when the 
vacuum exists, certain spring disks are separated, and the circuit is 
open ; the wires are so arranged that they cannot be tampered 
with without ringing the alarm. 

Mr. Gaffield read a paper on the " U. S. Weather Reports and 
Storm Signals for the benefit of Commerce," describing the in- 
struments used and the methods of observation, and showing how 
by this knowledge of a coming storm many lives and much valua- 
ble property can be saved. 

Feb. 16. Mr. Albon H. Bailey read a paper on a practical sys- 
tem of logotype composition to facilitate printing, substituting syl- 
lables and short words for the usual single-letter types. 

Mr. Brown explained some of the recent improvements in the 
type-setting machine of his invention. 

March 2. Mr. C. R. Cross gave a history of spectroscopy, and 
of its uses in Chemistry and Astronomy ; after which Prof. Picker- 
ing described the phenomena of the solar eclipse of Dec. 22, 1870, 
as observed in Spain by the American Expedition to which he was 
attached, giving an account of the experiments with the photo- 
meter by Mr. Ross, and with the polariscope — the general conclu- 
sion being that the corona is solar, and not terrestrial in its origin. 

March 16. Mr. James Hamblett, Jr., gave a description of Mr. 
Tilghman's process for etching on glass and stone by means of a 
blast of sand, driven by water or steam power. It is believed that 
this will find numerous applications in decorative and constructive 
art. 

Mr. Brayton exhibited in operation his compound gas engine, 
the power being derived from the expansion produced by the 



burning of a compound of atmospheric air and coal gas, in the 
proportion of 10 to 1. Its advantage is that it secures continuous 
combustion, without explosion and consequent necessity of con- 
stant re-ignition. 

April 6. Mr. H. McMurtrie read a paper, illustrated by a work- 
ing machine and by diagrams, on an automatic steam Vacuum 
Pump. 

Prof. Pickering described the Euharmonic organ, the invention 
of Mr. Allen, of Newburyport, in which temperament is done 
away with, and each musical note is given with absolute purity. 

April 20. Mr. E. "W. Bowditch described the various routes 
surveyed for an inter-oceanic canal across the Isthmus of Darien, 
and more particularly one to which he was attached last year, 
under Lieut. Selfridge, U. S. N. 

Mr. J. H. Gerry explained the mechanism of keyless or stem- 
winding and setting watches, and presented to the Institute a set 
of the mechanical movements for this purpose, invented by him- 
self, and used by the Howard Watch Co., of this city. 

May 3. Prof. Richards gave an account, with apparatus, of 
Bunsen's air or filter pump, drawing out air by a stream of water, 
by which the usually slow process of filtering is much accelerated. 

Mr. Gannett described the methods of determining longitudes or 
differences of time by the electric telegraph, showing their great 
accuracy. 

May 18. Mr. B. H. Locke, a student of the Institute, gave the 
methods of investigation and the results of a long series of experi- 
ments, made in the Physical Laboratory by himself and several 
other students, to determine the best coverings for steam pipes, to 
prevent radiation, and secure the most perfect transmission of the 
heat or the power of steam. Three pipes were used, one un- 
covered, one covered with a white cement furnished by the Sala- 
mander Cement Co., and the third with hair felt. The amount of 
water condensed per day in one foot of uncovered pipe was about 
4 1-2 lbs., in the cement covered pipe 2 1-4, and in the felt covered 
one 1 lb. ; in other words, the coal wasted per year would be in 
the three cases, 13,000 lbs. for the uncovered pipe, 7,000 for the 
cement, and 3,000 for the felt, per hundred feet of pipe. 



Prof. Pickering showed the results of some experiments made 
by Mr. W. T. Leman, a student of the Institute, on a new method 
of proving the law of falling bodies, by letting a plate of smoked 
glass fall in front of the prongs of a vibrating tuning fork, and 
then measuring the curves thus obtained. 

Prof. Watson exhibited a model of the Slide Valve, and showed 
by diagrams the mode of determining the lap and lead at any 
position of the crank. 

There have been elected during the year eleven associate mem- 
bers, the list now comprising 353 members. The re-organization 
of the Society of Arts, the adoption of its new code of By-Laws, 
and the regulation of its affairs by the Council, composed of the 
Committees on Communications, on Publication, on Membership, 
and on Finance, four committees of five each, have infused new life 
into its meetings ; and there has been no lack of interesting and 
valuable material, as the above abstract shows. When the objects 
of the Society are better known, there can be no doubt that all 
persons interested in the application of science to the useful arts 
will recognize its value as a tribunal before which to present their 

nventions and discoveries, and will be glad to increase its sphere 
of usefulness by joining its ranks. 

The Society invites all who have any valuable knowledge of 
this kind, which they are willing to contribute, to attend its meet- 
ings, and become members. All persons having valuable inven- 

i-ons or discoveries, which they wish to explain to an appreciative 
audience, will find a suitable occasion in the Society meetings, 
subject to proper regulations ; and, while the Society will never 
endorse, by vote or diploma, or other official recognition, any in- 
ntion, discovery, theory, or machine, it will give every facility to 
those who wish to discuss the principles and intentions of their 
own machines or inventions, and will endeavor at its meetings, or 
through properly constituted committees, to show how far any 
communications made to it are likely to prove of real service to 
the community. 



The School of Industrial Science has had a very prosperous and 
satisfactory year, 250 students having attended its sessions: 95 in 
the 1st year, 65 in the 2d, 45 in the 3d, 32 in the 4th, and the 
remainder special students in Chemistry, Drawing, and Architec- 
ture, including five females. Of these a little more than one-half 
are regular students ; more than two-thirds are from Massachu- 
setts, principally from Boston and vicinity. Thirty professors and 
teachers are connected with the School; the fees from students 
have amounted to over $31,000, nearly $6,000 more than last year, 
when the number of students was 224. 

The apparatus for instruction has been considerably increased ; 
a reading room and reference library have been opened under the 
supervision of a lady, and have proved a great success; a larger 
room and more books will soon be provided to make this depart- 
ment of the school what it should be. 

Beside the ordinary courses of the school, the Trustee of the 
Lowell Institute has established under the supervision of the In- 
stitute of Technology, courses of instruction, generally in the 
evening, open to students of either sex, free of charge. This year 
were given 

A course of eighteen lessons on Elementary French, by Prof. 
Bocher. 

A course of eighteen lectures on Physiology and Hygiene, by 
Prof. Kneeland. 

A course of eighteen lectures on Modern History, by Prof. 
Atkinson. 

A course of fifteen lectures on Descriptive Geometry, by Prof. 
Watson. 

A course of fifteen laboratory exercises in Chemistry, by Profs. 
Richards and Nichols. 

A course of ^fifteen laboratory exercises in Qualitative Analy- 
sis, by Profs. Nichols and Richards. 

These courses, which are intended to provide substantial teach- 
ing, rather than merely popular illustration of the subjects, have 
been well attended by persons coming with a serious purpose of 
improvement. The average attendance has been about 100. The 
new hall of the Institute, capable of seating about 1,000 persons, 
will be finished before the opening of the next session of the 



School, and will afford a very pleasant, commodious and accessible 
hall for the probably much larger audiences of the ensuing winter. 
The programme of subjects, and the extent of the courses, will be 
made known in October. 

In addition to the regular courses in Civil, Mechanical and Min- 
ing Engineering, Chemistry, Architecture, and Science and Litera- 
ture, provision has been made for a full study of Natural History, 
illustrated by the collections of the Boston Society of Natural 
History. Shorter courses will also be given preparatory for teach- 
ing Science, for business, special technical work and for the study 
of medicine, embracing Chemistry, Metallurgy, Physics, Natural 
History in all its branches, Physical Geography, Drawing, the 
Modern Languages, the use of the Microscope and of instruments 
of precision. 

Among the departments of the school which have assumed dur- 
ing the year large and very important proportions, may be men- 
tioned the Physical Laboratory. To establish a laboratory for 
teaching Physics experimentally, as Chemistry has long been suc- 
cessfully taught, had for years been the ardent desire of Prof. 
William B. Rogers, late President of the Institute of Technology, 
and before his retirement he had sketched and inaugurated a plan 
for such a laboratory at the Institute, the first in the country, 
since carried out and expanded by Prof. Edward C. Pickering, his 
successor in the Chair of Physics in the Institute. This has been 
in successful operation for two or three years, and is recognized by 
all progressive teachers of Physical Science as a great improve- 
ment in this department of education. That the Institute took a 
great and much needed step in advance, when it established its 
Physical Laboratory, is fully proved by the fact that similar La- 
boratories are springing up in various parts of the country, and 
probably will soon be attached to all the principal* colleges of the 
North and West. 

To show what the Institute's Physical Laboratory has done, and 
aims to do, Prof. Pickering's report is here introduced. 



Report of Prof. Pickering on the Physical Laboratory. 

In the Department of Physics the Institute was one of the first 
to adopt the Laboratory system, by which, in addition to attending 
the usual course of lectures on this science, each student performs 
a variety of experiments, and learns the methods, and to use the 
principal instruments of physical investigation. The system 
adopted during the last two years is this : A number of experi- 
ments are prepared, and the apparatus necessary for each is placed 
on a table, together with a complete written description. When 
the class enters the laboratory, each is assigned his place, by put- 
ting a card bearing his name opposite a second card representing 
the experiment. He then goes to the proper table, reads the de- 
scription, and perhaps completes the experiment without any aid 
from the instructor, who is thus left free to go from desk to desk 
and see that no mistakes are made. When an experiment is com- 
pleted, the pupil reports the result, the position of his card is 
changed, and he goes on as before. The number of experiments 
being always greater than that of the students, no delay is in- 
curred. When practicable, the results are represented graphically 
by drawing two curves on the same piece of paper, one represent- 
ing the numbers obtained by experiment, the other those com- 
puted by theory. Their agreement furnishes the most conclusive 
evidence of their correctness, and impresses on his mind the physi- 
cal law which they express. As examples of these experiments, 
we may refer to the measurement of the deflection of beams under 
varying loads, the conjugate foci of lenses, their curvature, specific 
gravity, wave lengths, the method of using the microscope, spec- 
troscope, polariscope, and meteorological instruments. 

In addition to these we always endeavor to have several investi- 
gations in progress, of which the experimental portion shall be 
performed by the students. Among those recently tried, are the 
calibration of a standard tenth of a cubic foot, the comparative 
delicacy of different polariscopes, and the hook gauge compared 
with a simple point for measuring the surface of a liquid. In this 
way the students learn to carry on investigations, while at the 
same time much valuable work is done ; and, being performed by a 
number of entirely unprejudiced observers, we get results free from 



8 

all personal bias, and in this respect preferable to any that could 
be obtained by a single experimenter. 

Our more advanced pupils also carry on more difficult researches ; 
during the last two months we have had a great many experiments 
made to determine what form of covering is best suited to protect- 
ing steam pipes from loss of heat by radiation. Similar pipes, 
covered with different materials, were subjected to steam of the 
same temperature and pressure, and the rate of cooling measured. 
Of course this was greatest in the uncovered pipe, and the per- 
centage in each of the others was determined. The same experi- 
ment was also tried with short pipes filled with boiling water. 
Next, the amount of water condensed in each in a given time* 
was weighed, and finally the volume received every minute, for 
half an hour, was measured. One of the students then collected 
the whole series of experiments, each of which is accompanied by 
a curve, and wrote a memoir explaining the whole subject, and 
showing what conclusions are to be drawn from them. Most of 
these experiments were performed by our students in Mechanical 
Engineering, and we intend next year to introduce for these stu- 
dents a regular course of experiments of this kind, including the 
pressure of steam at different temperatures, the strength of mate- 
rials, weighing and measuring of all kinds, adjustment of instru- 
ments, and all other branches of technical physics which relate to 
this profession. The mistakes often committed by a beginner do 
but little harm in a laboratory where they are easily corrected, 
while in actual practice they often involve much loss, both of time 
and money. So much is this the case that often, if a student ob- 
tained no result, his time would be profitably spent in teaching 
him what errors he must thereafter avoid. As an example of a 
different kind of research, another student has been trying a new 
method of measuring the velocity of falling bodies, by means of a 
tuning fork, which draws a curved line on smoked glass. He de- 
vised the apparatus, which was made under his direction at the 
Institute, then drew the curves, measured them with a microscope, 
and compared them with those given by theory ; and his instru- 
ment now becomes a valuable one to introduce in our regular 
course of physical manipulations. 

One of the most important objects of the laboratory is to pre- 



pare teachers of Physics. A large number of Institutions, where 
the value of a practical knowledge of the subject was realized, 
have applied to us for instructors, and we are very desirous of sup- 
plying this demand to the best of our ability. The course for such 
students would include the method of using ordinary lecture room 
apparatus ; the adjustment of instruments, planning of apparatus, 
and, when possible, overseeing its construction ; and finally the 
preparation of lectures, and proper methods of delivering them. 
They would, of course, be enabled to see how the regular lectures 
and laboratory exercises were conducted at the Institute, and, when 
they wished it, to assist in them. There is at the present time a 
great demand for good teachers of Physics, and the profession 
offers an excellent opening to any young man whose talents and 
inclinations lead him in this direction. 

Still another object of the Laboratory, and perhaps the most im- 
portant from a scientific point of view, is to afford professional 
physicists, and others engaged in conducting physical investiga- 
tions of any kind, the means of performing their experiments at 
the Institute. The want of apparatus prevents almost any indi- 
vidual from doing much work of this kind, which can easily be 
performed in a laboratory properly supplied with water, gas, steam, 
and other appliances commonly needed. As instances of this kind 
of work, we may mention some experiments now in progress- to 
determine accurately the change in elasticity of iron due to mag- 
netism, and our expectation of an elaborate series of measure- 
ments of the strength of different forms of electro-magnets; 

The Laboratory has heretofore been treated as an experiment, on 
which, therefore, but little money has been spent. The method, 
however, proving so successful, and being adopted in so many In- 
stitutions, both at home and abroad, enables us now to look at it 
from quite a different point of view. What is now needed is the 
means of procuring instruments of precision, by which all the 
higher portions of the subject may be treated, and with which stu- 
dents may make their measurements with all the accuracy needed 
in real observations. It was feared that the injury to such appar- 
atus from rough handling would be very great, but experience has 
shown that we have little to apprehend from this source. We 
have obtained during the past year an admirable collection of 



10 



apparatus of this kind for measuring electrical resistances, suitable 
for instructing students in almost all the questions which may oc- 
cur in connection with submarine cables. 

Apart from their practical importance, these experiments have 
another value of quite a different kind, namely, as a means of 
general culture*. Besides illustrating certain physical laws, they 
show the student how these laws are obtained, the true relation 
between theory and practice, and by what processes of reasoning 
our knowledge of physical science was acquired. But it is un- 
necessary to dwell further on these matters, as they appeal not 
merely to the professional Physicist, but to all believers in the im- 
portance of a sound knowledge of applied science. 

The Department of Mechanical Engineering has also received 
important additions during the year, and the facilities offered to 
students will be understood from the following 

Report on the Museum op Descriptive Geometry and 
Machinery, by Prof. William Watson. 

The collections of this Museum consist of models in wood, in 
metal and in plaster, besides lithographs, photographs and manu- 
script drawings, chiefly selected from the best collections of France, 
Germany and Switzerland, and, in some instances, made expressly 
for the school. They may be grouped as follows : — 

Plaster Models. 

I. Descriptive Geometry, and its applications to Shades, Shadows 

and Linear Design. 

1. A set of models in relief, illustrating the proper use of light 
and dark lines in linear design. 

2. A set of models illustrating the theory and practice of shades 
and shadows. 

3. A set of models showing the sections of single curved, 
double curved, and warped or twisted surfaces. 

4. A set of models showing the intersections of cylinders, cones, 
and surfaces of revolution with each other, the penetrations made 
in each surface and the common solid. 



11 



II. Masonry and Stone Cutting. 

1. Plate bands. 

2. Full centred, segmental, conical, conoidal and annular 
arches. 

3. Portals, right, oblique, and rampant. 

4. Niches. 

5. Trompes and brackets. 

6. Domes. 

7. Spiral, suspended, and covered staircases (vis /Saint Gilles.) 

III. Experimental Mechanics. 

1. Casts of Saint Vennant's models, showing the changes of 
forms which bodies of various shapes undergo, when subjected to 
forces causing flexure and torsion. 

2. A full sized model of the liquid vein observed and meas- 
ured by Poncelet and Lesbros, in their hydraulic experiments. 
These models are duplicates of those made for the Conservatoire 
des Arts et Metiers, at Paris. 

IV. Graphical Representation. 

1. A model representing the mean temperature of a place for 
the twenty-four hours of each day of the twelve months of the 
year. 

2. Topographical models, showing contour lines, with accom- 
panying topographical drawings. 

Modelling in Pasteboard. 

The instruction in Descriptive Geometry is practical as well as 
theoretical. When the drawings relating to the intersection of 
developable surfaces are completed, the students cut patterns of 
these surfaces, and rolling or folding them together produce the 
exact solids in space, with the apertures formed by the passage of 
a portion of one solid through the other. A considerable number 
of models thus made have been added to the collection. 

Modelling in Plaster, (Descriptive Geometry.) 
The graphical solutions of problems relating to the sections and 
intersections of doubled curved surfaces are applied to solids in 
plaster, prepared expressly for this purpose, and the students are 
required to execute their solutions in relief. 



i 



12 



Modelling Tools, Moulding and Modelling in Plaster. 

(Stereotomy.) 

Sets of modelling tools have been provided and practical exer- 
cises in stone cutting are given ; these consist in executing from 
rough pieces of plaster, models of portals, arches, domes, staircases, 
bridges, etc., with the aid of drawings and patterns previously pre- 
pared by the students themselves : in this way the collections have 
been increased to some extent, and it is thought that the practical 
skill and familiarity with the details of construction thus acquired, 
will ultimately be of signal service to the student in the subsequent 
practice of his profession. 

Moulding in plaster is also taught to a limited extent. 

Models in Wood or Metal. 

I. Descriptive Geometry. 

1. A set of models to illustrate Descrij>tive Geometry with 
Schroder's construction plates. They consist of models in relief 
of the various problems of Descriptive Geometry, arranged upon 
sets of planes at right angles to each other, and containing the 
corresponding graphical solutions. 

2. Models executed in brass and silk threads to illustrate the 
course on developable and warped surfaces. 

II. Carpentry. 

1. Models of joints and mouldings. 

2. Models of roof trusses in wood and iron, including a model 
illustrating Polonceau's system of iron roofs, centres for bridges, 
girders, etc. 

3. Models of bridges. 

III. Mechanism. 

1'. Models showing the different methods of laying out teeth of 
wheels in the various cases of racks, outside and inside gearing, 
etc. Bevel and skew bevel wheels. 

2. An instrument for laying out teeth devised by Schroder. 

3. Models of pulleys and wrapping connectors, belts and chains. 

4. Models of parallel motions, including Watts' parallelogram, 



13 



applied to land and marine engines. Seward's parallel motion, 
fitted to the engines of the Gorgon, etc. 

The foregoing models in mechanism were presented by Hon. 
E. B. Bigelow, of Boston. 

5. Models of non-circular, and screw wheels. 

6. Endless screws. 

7. Wheels in trains ; epicyclic trains ; Ferguson's paradox ; 
equation clock ; system of Lahire, etc. 

8. Models of cams. 

9. Models of silent feed motions. 

10. Models of quick return motions. 

11. Regulating apparatus, i. e., apparatus for stopping, reversing 
or modifying the motions of machines. These include governors, 
friction cones and clutches, reversing gear, Oldham's coupling, etc. 

IV. Resistance of the Materials used in Construction. 
A set of models illustrating the best forms of beams for resist- 
ing flexure, torsion and compression under various conditions of 
stress ; to which is added an apparatus for testing the deflections 
caused by loads applied in any manner to test their strength or 
stiffness. This collection, made Schroder, is the gift of Hon. E. B. 
Bigelow. 

V. Construction of Machines. 

These consist of a number of highly finished models made by 
Schroder, and presented by Hon. E. B. Bigelow. They include 
models of the parts of machines, such as screws, chains, hooks, 
riveting, axles, plumber blocks, steps and supports for shafts, wheels, 
pulleys, cranks, eccentrics, cross-heads, connecting rods, working 
beams, valves, pistons, etc. 

VI. Lifting Engines. 

Including the following working models : 

1. Crab engine. 

2. A complete model of Fairbairn's plate iron dock crane ; 
presented by Hon. E. B. Bigelow. 

3. Hydraulic press. 



14 



VII. Hydraulic Motors. 

1. A model of the water pressure engine at Alt Mordgrube, 
in Freiberg, Saxony, with the pumps and apparatus for draining 
mines. 

2. A model of Ponceletfs water wheel. 

3. A model of Fourneyron's turbine ; presented by Hon. E. B. 
Bigelow. 

4. A model of Jonval's turbine. 

5. Swain's and Leffel's inward flow turbines. 

VIII. Steam Engines. 

1. Boilers and Fire grates. 

2. Steam cylinders, pistons, valves, etc. 

3. Slide valves and the mechanism, showing the distribution of 
the steam. 

4. Variable cut-off valves — Stephenson link motion. 

5. Models of steam engines of various forms. 

Use of the Models. 

The foregoing enumeration would be incomplete without some 
reference to the use made of the models and the methods of in- 
struction in the Department of Mechanical Engineering. 

Besides the ordinary lectures and recitations, there are, in this 
department, two distinct kinds of instruction ; the first is that giv- 
en in the drawing rooms in making sketches and finished draw- 
ings of machinery from models ; the second is the practical instruc- 
tion by projects. These projects, given in connection with the 
lectures and complementary to them, are of three kinds. The pro- 
jects of the first kind comprise those in applied Cinematics, having 
for their object to determine from the graphical representation of 
the motion, the form adapted to each piece of mechanism. 

Two or three examples taken from the actual work of the stu- 
dents are here inserted as illustrations : 

Cams. Show how to construct a cam which shall give any assigned mo- 
tion to a moving piece. Given s =f(f). 

Example. Make a cam which shall give exactly the motion of an eccen- 
tric, with a throw of ten inches. 

Beoel Wheels. Two axes intersecting at an angle of 80° are to be con- 
nected by a pair of bevel wheels : one axis is required to make three revo- 



15 

lutions to one of the other. The largest radius of the pinion is 12 in.; this 
pinion is to have 44 cast iron teeth. The teeth of the wheel are to be of 
wood, and the width measured along the pitch surfaces is to be 5 in. The 
profiles of the teeth are to be involutes of the circle ; and finally there must 
always be at least one pair of teeth on the first in contact with a pair on the 
second wheel. Show how to lay out the teetn. 

Skew Bevel Gearing. It is required to connect two perpendicular axes 
not situated in the same plane by a pair of skew bevel wheels. The shortest 
distance between the axes is 12 in.; the least diameter of the pinion must 
be 24 in.; it must have 72 teeth 6 in. in width, measured along the pitch 
surface. The profiles of the teeth are to be formed by epicycloids and hy- 
pocycloids. 

Valve Gear. In a simple slide valve gear, let the eccentricity be 2.3 in., 
and the angle of lead 30°. Let the steam be cut off at .8 of the stroke, and 
let the release take place at .96. It is required to find the inside, and out- 
side lap and lead, the greatest opening of the ports, and the opening of 
each port corresponding to any position of the crank. 

The students are required to present full sized working drawings 
together with a memoir containing the description, the theory and 
practical details of the work. 

These projects include the construction of cams, eccentrics, link - 
work, and all kinds of gearing. Projects of the second kind are 
exercises in the construction of parts of machines, such as axles, 
cranks, valves, pistons, and finally of complete machines, from nu- 
merical data. And for this purpose, liberal use is made of the col- 
lections furnished by Mr. Bigelow, and enumerated above. 

Projects of the third kind are not given until the students have 
been made acquainted with the doctrine of the strength of materi- 
als, so as to be able to find the dimensions of pieces to resist flex- 
ure, shearing, torsion, etc. They consist of original designs for 
machines, involving the determination of the strength, dimensions, 
and proper proportions of the several parts by calculation. 

The following are some of these projects : 

1. Project for a travelling crane to be employed in the con- 
struction of a stone bridge. 

2. Project for a hydraulic foundery crane to raise twenty tons. 

3. Project for a turbine, having given the fall and the volume 
of water. 



LIBRARY OF CONGRESS 



030 008 425 4 



4. Project for a set of boilers for a pumping engine of 300 
horse power. 

5. Project for a rolling mill driven by a steam engine. 
These projects comprise — 

1. The plans, elevation* and sections of the machines. 

2. The working drawings of the details. 

3. A memoir containing the description and theory of the ma- 
chines ; the estimation of the resistances ; the calculation of the 
strength and proper proportions of the parts, and the reasons for 
the particular dispositions adopted. 

Much value is attached to these last exercises, and the whole o 
the previous work is made tributary to them. 

In conclusion, attention is called to the three-fold use of these 
models; first, in the drawing rooms as objects from which sketches 
and finished drawings are made ; second, in the lecture rooms, to 
illustrate the principles of machinery, and to exhibit to the eye 
what would otherwise require long and tedious explanations ; and 
third, in the practical exercises in construction and design, which 
would be difficult, if not impossible, without them. 



Sixteen students successfully passed the examinations for de- 
grees, and will receive their Diplomas on presentation of accepta- 
ble theses in September. 

In 1868, there were 27 applicants for admission to the School of 
the Institute; in 1869, 32 ; in 1870, 37; and this year, 58. 

June 15, the President, four Professors, and fifteen of the grad- 
uates and fourth year's students in Mining Engineering and Metal- 
uurgy, started for Colorado, to spend the vacation in examining 
mines and metallurgical processes, chiefly in Colorado ; the iron 
region of Missouri and the mines of Utah will also be visited. 
This is not a pleasure excursion, but an expedition for systematic 
work ; the students will make reports of their special investiga- 
tions, which, with those of the Professors, will hereafter be sub- 
mitted to the Corporation, giving, it is believed, important results 
in relation to the mineral wealth and economic processes of the 

regions visited. 

Respectfully submitted, 

SAMUEL KNEELAND, Secretary. 
Boston, June 16, 1871. 



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